There is critical and continuous need for research to develop and evaluate the efficacy of surgical treatment for voice disorders. Of particular interest are pathologies related to scarring for which there is no satisfactory treatment. This project proposes to develop optimization criteria for phonosurgical treatment of scarring respresented by sulcus vocalis. This will be accomplished through a unique mixture of 1) clinical and surgical trials, 2) histological studies, 3) laboratory experiments, and 4) computer modeling. The laboratory experiments will investigate phonosurgical outcomes on both an excised larynx set-up, and on a physical model of the larynx (e.g., the vocal fold tissues, the sulcus, and the surgical scarring will be represented by a variety of biomaterials designed to simulate the histological properties). As a function of sulcus depth and position, document changes in a) phonation threshold pressure, b) amplitude of vibration, c) degree of glottal closure, d) mucosal wave velocity, e) mucosal wave shape, f) glottal airflow, and g) acoustic output; 2) quantify the fibrous and interstitial proteins and the dynamic viscosity, elastic shear modulus in scarred and sulcus vocalis vocal fold tissue; 3) quantify the influence of the viscoelastic properties of the pre- and post-operative tissues associated with scarring and sulcus vocalis on vocal fold vibration; 4) simulate and optimize four phonosurgical procedures (injection, sulcus excision, sulcus excision plus injection, mucosal slicing, and thyroplasty) for correction of scarring and sulcus vocalis. This study, combining both clinical/surgical trials and systematic laboratory investigations, is extremely timely because no consistently effective treatment modality is known for sulcus vocalis. Indeed, treatment of this voice disorder is one of the unsolved problems of modern phonosurgery (Hirano et al, 1990).